Apparatus for flattening and for constraining the expansion of preflattened coiled tubing



Se t. 3, 1957 J. K. M DUFFEE 0 APPARATUS FOR FLATTENING AND FOR CONSTRAINING THE EXPANSION 0F PREFLATTENED COILED TUBING Filed March 24, 1954 IAIVENTOR J. K. M "DUF [E B) ArrbR'A/sr nited APPARATUS FOR FLATTENENG AND FOR CON- STRADQING THE EXPANSION F PREFLAT- TENED COILED TUBING Application March 24, 1954, Serial No. 418,431

2 Claims. (Cl. 153-32) This invention relates to bending tubing and particularly to bending hollow tubing to a desired configuration without kinking.

In bending tubing such as copper tubing for water cooled induction heating coils it is diflicult to avoid kinking especially when bending the tubing to small radii or complicated configurations.

Heretofore, such bending has been accomplished by utilizing special mandrels or fillers in the tubing while bending, thereby preventing the collapse or kinking of the walls of the tubing. Such means are not, however, well adapted for the bending of tubing to complicated shapes or to different cross-sectional dimensions than the tubing had initially.

It is, therefore, the object of this invention to provide a simple method and apparatus for changing the shape and cross-sectional dimensions of hollow tubing.

In accordance with the present invention, the crosssectional dimension of the tubing is reduced to less than the desired cross-section by flattening and then fluid pressure is applied to the internal surface to reopen the flattened tubing while the outer surface is constrained to limit the re-expansion to the desired cross-section.

To bend tubing to a desired configuration without kinking, the tubing is first bent to the general configuration desired then flattened to a cross-section less than the desired cross-section or conversely, the tubing could first be flattened then bent to the desired shape and then the bent, flattened tubing is re-expanded while constraining the outer surface to limit the re-expansion of the tubing to the desired cross-section.

A preferred embodiment of the invention for constraining the expansion of pre-flattened, bent tubing for water cooled induction heating coils utilizes a pair of end plates each having a constraining surface for one of the end turns of the coil, means for mounting the plates in fixed space relation whereby the constraining surfaces are mutually parallel, spacers of predetermined thickness, having split portions for constraining the expansion of tubing interconnecting successive turns of the coil, for constraining expansion between successive turns of the coil and a constraining mandrel for the core of the coil.

These and other features of the invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawing in which:

Figs. 1, 2 and 3 are plan, side elevational and front elevational views respectively of a two turn, water cooled induction heating coil formed according to the invention;

Fig. 4 is a view of the coil along the plane of line 4-4 as seen in Fig. 1 showing the constraining split spacer in cross-section;

Fig. 5 is a side elevational view of a fixture for constraining the expansion of the tubing to produce the coil of Fig. l;

" atet ice Figs. 6 and 7 are plan and side views respectively of the split spacer used in the fixture of Fig. 4.

Referring now to the drawing, apparatus is shown for forming an induction heating coil whose turns 8 and 9 are of a general flattened, elliptical cross-section as shown in Fig. 4. Such a configuration is desirable as it provides for high current density such as is required for concentrated induction heating and yet has a large cross-sectional area for thepassage of coolant.

It is also desired with this particular induction coil to concentrate the heating effect to the vicinity of each of the separated turns of the coil. It is, therefore, necessary to sharply bend the inter-connecting tube 10 between the two turns while still providing substantially a full 360 of tubing for each turn.

To utilize the present invention in producing the above coil, round copper tubing is wound around mandrel 11 of the fixture of Fig. 4, (the mandrel being removable from the fixture) to the general shape of the coil. The diameter of the mandrel 11 is equal to the desired core diameter for the coil. The coil thus formed is then flattened by any convenient means such as by hammering or pressing. This may be done in the fixture by loosening the clamping screws 17 and 18 on which end plates 19 and 20 are mounted, one (plate 19) or both of which may be slidably mounted thereon. The roughly formed coil which may be kinked, is then removed from the mandrel 11, the split spacer 16 is inserted between the coils 8 and 9 so that the portion 10 inter-connecting turns 8 and 9 lies between the split opening 27 of the spacer. This assembly is thereupon inserted between the parallel surfaces 14 and 15 of plates 12 and 13 respectively when mandrel 11 is inserted in a hole provided therefor in end plate 19 and plates 12 and 16 so that it passes through the coil and the spacer and rests on surface 15 of plate 13. The nuts 22 and 23 on clamping screws 17 and 18 respectively are first tightened until the coils 8 and 9 are flattened and then loosened to a predetermined location on the screws which determines the final expansion of the tubing. The ends 24 and 25 of the coil are then connected to a fluid pump in a conventional manner, the size of the fluid pump depending upon the size and material of the coil, and fluid pressure is applied thereto to reopen the flattened tubing while the spacer 16, mandrel 11 and plates 12 and 13 limit the expansion thereof to the desired dimensions; The fluid pressure is then relieved, the coil is disconnected from the fluid pump, the mandrel 11 is withdrawn from the fixture, spacer 16 is removed from the coil and the completed coil is withdrawn from the fixture.

While the invention has been described with respect to the particular embodiment for purposes of illustration, it will be understood that the device or the method could be modified in various ways in accordance with the general principles of the invention and the requirements of the particular conditions of use. For example, it may be desired merely to re-expand a flattened tubing to a desired cross-section configuration without bending to any particular shape such as a coil as described. in other cases where the tubing is required to be bent to various configurations it may be simpler to first flatten the entire length of tubing prior to bending to the configuration desired. Numerous other arrangements may be devised by those skilled in the art which will embody the principles of the invention and follow the spirit and scope thereof.

What is claimed is:

1. Apparatus for flattening and for constraining the expansion of preflattened coiled tubing into coils having parallel turns of substantially 360 each and the tubing of the turns having a generally elliptical cross-sectional shape, comprising a pair of relatively movableend plates,

means for mounting the plates in fixed space relation, said plates having opposed, parallel constraining surfaces for the end turns of the coils, a constraining mandrel for the drical constraining mandrel for the core of the coils, and a removable spacer of predetermined thickness for separating the turns of the coils, the spacer having an aperture therethrough for the mandrel and a split passage for the core of the coils the shape oi the cross-section ofiwhich 5 tubing interconnecting the turns of the coils.

is similar to the desired-expanded core cross'seetion of the coils, and removablespacefs of predetermined thickness for separating the turns of the coils,- eachspacer having an aperture theret'hroug'h for the natandrel and aiisplit passage for the tubing interconnecting successive turns of the coils. I V

2. Apparatus for flattening and for constraining the expansion of. preflattened', two-turncoiled tubing'i-nto coils having two parallel turns of substantially 360 each and the tubing of the turns having a generally elliptical" cross-sectional shape, comprising'arpair of relativelymov-- able end plates, means for: mounting the plates infixed space relation, said plates having opposed, parallel constraining surfaces for the end turns of the coils, a cylin- References Cited in the file of this patent UNITED STATES PATENTS 1,455,188 Cox May' 15, 1923 1,542,983 Bergmann June 23, 1925 2,229,462 Kurtz Jan. 21, 1941 2,296,451 Roberts Sept. 22, 1942 FOREIGN PATENTS 570,251 Germany Feb. 13, 1933 469,004 Great Britain July 16, 1937 624,227 Great Britain May 31, 1949 

